The dangerous dentition of the dromedary consists of extremely modified incisors, not canine teeth

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The dromedary (https://www.inaturalist.org/taxa/81542-Camelus-dromedarius) is unusual among domestic ungulates, in its ability to inflict mutilating bites on humans (https://www.sciencedirect.com/science/article/abs/pii/S0278239197903037).

Furthermore, the injuries are surprisingly complex (https://www.cureus.com/articles/76751-camel-bite-injury-to-the-face-in-an-adult-patient-skin-closure-controversy#!/ and https://pubmed.ncbi.nlm.nih.gov/22186231/ and https://www.omicsonline.org/open-access/camel-bites-a-unique-experience-2329-6879.1000192.php?aid=39310 and https://www.sciencedirect.com/science/article/abs/pii/S0020138311005328 and https://journals.lww.com/njms/Fulltext/2015/06020/Camel_bite_An_uncommon_mode_of_maxillofacial.7.aspx and https://journals.lww.com/njms/Fulltext/2015/06020/Camel_biteAn_uncommon_mode_of_maxillofacial.7.aspx and https://www.researchgate.net/publication/276389211_Camel_Bites-A_Unique_Experience and https://www.researchgate.net/publication/51879246_Camel_bite_injuries_in_United_Arab_Emirates_A_6_year_prospective_study and https://journals.lww.com/njms/Fulltext/2015/06020/Camel_bite_An_uncommon_mode_of_maxillofacial.7.aspx).

For example, according to https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4922227/:

"Due to large jaws size camel engulfs the head of the victim and crushes it like a 'nutcracker' resulting severe soft tissue and skeletal injuries to face...Typical of camel bite is that whole face is crushed between two strong jaws resulted into compression and crushing type of injury, which is surprising and different from any other animal bite."

The purpose of this Post is to show that it is the incisors, not the canines, of the dromedary that are unusually specialised for aggressive/defensive biting.

The anterior dentition of Camelidae can be bewilder zoologists (https://www.researchgate.net/publication/303857725_History_of_dentition_in_camels). In both sexes of adults of the dromedary, the four lower incisors are heterogeneous in form and function.

DIFFERENTIATING INCISORS FROM CANINES

I can explain the dentition of the dromedary with reference to the clearest photos available on the Web, as follows.

In each case I proceed from anterior to posterior on a given side (right or left), first for the upper jaw, and second for the lower jaw. I consider only the adult (permanent) dentition, not the milk (deciduous) dentition.

I begin with the following of an adult male individual (https://upload.wikimedia.org/wikipedia/commons/b/b1/Camelus_dromedarius_skull.jpg):

The anterior-most upper jaw is seen to be toothless. Incisors 1 and 2 have been lost evolutionarily, and replaced by a horny, bare pad (https://www.gettyimages.co.uk/detail/news-photo/pakistani-man-checks-the-teeth-of-a-camel-at-an-animal-news-photo/456193758?adppopup=true and https://www.gettyimages.co.uk/detail/news-photo/trader-shows-his-camels-teeth-at-a-livestock-market-set-up-news-photo/601774900?adppopup=true), similar to that of true ruminants. Most food is 'bitten' off by closing the three (6 if both left and right are considered) anterior-most lower incisors (which are spatulate rather than caniniform) against this toothless pad.

What this means is that, in the case of incisors 1 and 2 on the upper jaw, and incisors 1, 2, and 3 on the lower jaw, the dromedary is unremarkable, and similar to true ruminants. Even if this dental apparatus were used to bite an enemy, it would hardly be injurious, because there is no possible dental occlusion.

Continuing with the adult male (https://upload.wikimedia.org/wikipedia/commons/b/b1/Camelus_dromedarius_skull.jpg ):

The anterior-most teeth on the upper jaw are incisors 3 and 4. Both are stoutly caniniform, with 4 being larger than 3. Both show potential for aggressive/defensive biting, along the lines of Carnivora such as Panthera. However, they do not look particularly sharp/pointed.

Proceeding on the upper jaw, the next tooth, after a wide diastema (https://www.google.com.au/search?sxsrf=APwXEdeCq5b5stsY8L6E0t3QUC5oTC1mYA:1683328695130&q=diastema&si=AMnBZoFvNU0WynupgJGHQVzk85f5SygBC8IFGoglJKEiaBoxIykLSU9KM8YbOwoBJO_C8sThA8nPUYqirRxSgPA447CRFUPq9PavS3Hu-tQ-Jxkz86-zMWs%3D&expnd=1&sa=X&ved=2ahUKEwirjaeHqN_-AhXj6zgGHSGWAKcQ2v4IegQICBAT&biw=1013&bih=552&dpr=2.7), is the upper canine.

The upper canine is similar to the canines of Carnivora, but the points to note are that

• it is smaller than the caniniform incisors, and
• it is located so far back in the jaw that it its potential for injurious biting is limited.

Now, turning to the lower jaw in the same photo, viz. https://upload.wikimedia.org/wikipedia/commons/b/b1/Camelus_dromedarius_skull.jpg :

The first tooth located posterior to (with no diastema) the three spatulate incisors is incisor 4. What is surprising is that this incisor is somewhat caniniform.

Please note that lower incisor 4 fits between two upper teeth with similar caniniform shape, viz. upper incisors 3 and 4. This implies a capacity for not only piercing but also clamping.

The next tooth on the lower jaw, after a large diastema, is the lower canine. This mirrors its upper counterpart, and once again shows limited capacity for injurious biting, owing to its size and position. In particular, please note that the upper and lower canines are too short to reach each other, even when the mouth is fully closed.

Posterior to the canine teeth on both the lower and the upper jaw, there is a wide diastema before the molariform teeth are reached.

Because of the extreme flexibility of the gape, the molariform teeth could, in principle, be used to inflict a crushing bite on an enemy, in a way impossible in tight-mouthed ruminants such as giraffes. Also, please bear in mind that the normal bite of Diceros bicornis (https://www.alamy.com/stock-photo-diceros-bicornis-black-rhinoceros-skull-gallery-of-paleontology-and-59339980.html?imageid=9535B17E-6405-4E00-9794-559A1DABBC39&p=258772&pn=1&searchId=d43c3c58c0d9e1b13d43bc96739a3a84&searchtype=0), in which it routinely clips woody stems about 1 cm in diameter, is by means of the molariform teeth.

However, it is unlikely that the dromedary would resort to biting aggressively/defensively by means of the molariform teeth, because there are so many caniniform teeth far closer to the front of the mouth.

Now, turning to an adult female individual (https://commons.wikimedia.org/wiki/File:Camel_skull_02.jpg).

This differs from adult males in that

• all the caniniform teeth are relatively small,
• two of the upper caniniform teeth, including the canine itself, have been lost with wear/age,
• the lower canine is so small, and slanted, that it seems to have lost any capacity for injurious biting, and
• the remaining relevant teeth are upper incisor 4 and lower incisor 4, which deeply occlude in a way suggesting
• sharpening of the lower, more blade-like incisor on the upper, longer and more pointed, incisor.

The important point about adult females is that, despite the reduction of the caniniform dentition relative to males, there is an upper/lower pair of caniniform incisors with an obvious capacity for injurious biting, by means of piercing and cutting/pincing/slashing.

Let us now refine this description, by examining another adult male individual (https://fineartamerica.com/featured/1-dromedary-camel-skull-millard-h-sharp.html).

Once again, the anterior-most toothlessness (upper) and spatulately incisiform teeth (lower), which are used in foraging, are clearly shown.

When it comes to the caniniform (but fairly blunt-looking) incisors, please note that lower incisor 4 occludes with upper incisor 4 in such a way that there seems to be a honing mechanism. In this sense, these canine-like teeth differ from those of Carnivora and somewhat resemble those of Suidae (https://a-z-animals.com/blog/wild-boar-teeth/) and Papio (https://twitter.com/AnaCarolina_Art/status/1349410432877006864).

These incisors seem adapted as much for slicing/pincing as for piercing.

In the case of the canines, please note that the lower is larger than the upper, and that the tips meet when the mouth is closed. However, once again there is so little scope for occlusion that the canines have limited capacity for injurious biting. They can provide extra grip on a large object such as a human head, rather than doing most of the mutilation.

My final illustrations, for adult males, are as follows (https://www.mediastorehouse.com.au/ardea-wildlife-pets-environment/kel-1213-5274232.html and https://www.sciencephoto.com/media/1009953/view/dromedary-camel-skull).

In these cases, please note that even upper incisor 3 has a honing mechanism, on lower incisor 3. This, once again, suggests that the use of the caniniform incisors is for slicing/pincing, as much as for piercing.

DISCUSSION

The dromedary possesses upper caniniform teeth, superficially resembling the canines of Carnivora. The fourth upper incisor is visible in the following expression, reminiscent of the 'fang-bearing' expression of felids (https://www.alamy.com/closeup-of-a-camels-head-and-open-mouth-image60186624.html?imageid=BD728EB3-A595-4542-9F76-AE7D81168649&p=191433&pn=1&searchId=e70747166a9108431a14954f9ac91060&searchtype=0 and https://www.gettyimages.co.uk/detail/photo/camel-with-open-mouth-royalty-free-image/478539813?phrase=camel+teeth&adppopup=true).

However, the most hazardous tooth seems to be the relatively inconspicuous fourth lower incisor, which is present in both sexes albeit small in females.

It is this tooth, I suspect, that enables the dromedary, in extreme cases, to decapitate a human victim over a period of several minutes (https://www.dailymail.co.uk/news/article-3604619/Camel-bites-owner-s-HEAD-left-tied-sweltering-heat-day.html).

In this sense, it seems that the incisor armament of the dromedary is somewhat analogous with the carnassial dentition of Carnivora (https://en.wikipedia.org/wiki/Carnassial).

The fourth lower incisor fits - like an inverse triangle - between two upper teeth, viz. the third and fourth incisors, allowing the side-to-side movements of rumination (https://mixkit.co/free-stock-video/camel-chewing-his-food-6870/ and https://www.youtube.com/watch?v=3yYgdrmC7xY and https://www.youtube.com/watch?v=VRWzdKzqdxI and https://www.youtube.com/watch?v=8J5cDMrsiQ8 and https://www.youtube.com/watch?v=k5-O8qTQYmM and https://www.youtube.com/watch?v=sC7SDGzwUjQ and https://www.youtube.com/watch?v=OsoJ2MtbwW0).

However, at other times, with slight adjustment of the jaws, it can also be honed. This is against the fourth upper incisor in particular.

The dromedary thus has the ability to cut objects by means of the fourth lower incisor. However, it probably never uses this while foraging.

Furthermore, when the dromedary takes a human head into its mouth in anger,

• the lower jaw of the human victim seems particularly vulnerable, owing to the upwards action of this tooth, and
• on a smaller scale, and with a narrower bite, the skin and flesh of the victim can probably be mangled and sliced, by working the fourth lower incisor against the third and fourth upper incisors.

What is odd about injurious biting by the dromedary is its combination of

• piercing by caniniform incisors (analogous but not homologous with Carnivora),
• slicing/shearing by incisors that are not used to slice or shear food, and
• application of great bite-force even with the mouth wide open (to the degree of fracturing a human cranium).

The following show how widely the dromedary can open its mouth (https://www.dreamstime.com/royalty-free-stock-photos-camel-mouth-open-wide-image22659368 and https://www.alamy.com/stock-photo-camel-yawning-39032884.html?imageid=2AED7279-910E-435C-B34A-2A3686228BBD&p=67088&pn=1&searchId=e70747166a9108431a14954f9ac91060&searchtype=0).

In this way, the dromedary is extremely different from giraffes, which can open the mouth to a remarkably limited extent (https://www.istockphoto.com/photo/yawning-giraffe-gm145192923-5374061?phrase=giraffe+yawning and https://www.saczoo.org/wp-content/uploads/2007/08/8-15-07004-1.jpg and https://www.istockphoto.com/photo/giraffe-yawning-gm122995554-16661938?phrase=giraffe+yawning).

(Also see https://www.youtube.com/watch?v=A8CUBOH1zTs, which is probably misconceived)

The configuration of dentition and jaw musculature seen in the dromedary is, as far as I know, unique among mammals.

I have yet to investigate

• whether South American camelids have dentition similar to that in Camelus, and
• how the jaw muscles are adapted to apply force with the mouth wide open, which is impossible in true ruminants.

FURTHER ILLUSTRATIONS

https://www.alamy.com/stock-photo-a-camel-shows-its-teeth-while-bellowing-at-tourists-near-the-ruins-25666900.html?imageid=48063F49-FD6A-4D45-BFDF-9CB671E1D103&p=69169&pn=1&searchId=e70747166a9108431a14954f9ac91060&searchtype=0

https://www.shutterstock.com/it/image-photo/camel-teeth-head-761596021

https://www.alamy.com/stock-photo-camel-teeth-16258655.html?imageid=8E35C3E5-AFA5-445B-8D16-C7C0C6E63842&p=288835&pn=1&searchId=e70747166a9108431a14954f9ac91060&searchtype=0

https://www.alamy.com/an-angry-camel-opens-his-mouth-to-show-his-yellow-teeth-and-bad-breath-in-the-northern-territory-australia-image333783903.html?imageid=97E30379-306C-4140-A558-F965904842FF&p=340903&pn=1&searchId=e70747166a9108431a14954f9ac91060&searchtype=0

Posted on Μάιος 05, 2023 0908 ΜΜ by milewski